Safari 5.0.4 sluggish

Question

Hi there,
Has Safari's performance started to feel occasionally sluggish to you?
By this I don't mean loading webpages, but rather general application slowness, spinning balls, hanging, etc.
Websites seem to load just fine. No problems there.
It's the actual program that has started to feel heavy and sluggish when typing URLs, filling forms and closing tabs, for example.
Recently, I've been experiencing a very noticeable lag when filling forms: I'll start typing into one field and then hit tab to switch to the next and sometimes it will take Safari 3-4 seconds to do it.
I've also noticed that Safari will occasionally take a few seconds, maybe even produce a spinning ball for a while, just to close a tab.
One behaviour that I can consistently reproduce is sluggish typing of URLs. I'll open safari, start typing the URL for a website I want to open, pick the Top Hit in the smart address bar, hit Enter to start loading the website, open a new tab while the previous one is still loading and start typing the URL for the next website and so on. Typing the URL will now become sluggish and grind to a halt by the second or third tab.
Now, I've noticed that this tends to happen more with heavier websites (especially Flash-heavy sites).
Before you hit me on the head and say that Safari is simply coping with the resource-intensive websites I'm loading in the background, let me just add that this happens EVEN if I disable all plug-ins (Flash included) through Safari's preferences.
My computer is a late 2007 MacBook, but it has always run very smoothly and I upgraded the RAM to 4 GB and installed Snow Leopard last year, which made it noticeably snappier, so I couldn't be happier with its performance.
I've tried all the Safari maintenance procedures (reset it countless times, moved plists, caches, metadata files, favicons, bookmarks, etc.) and in my 'Internet plug-ins' folder I have only your standard plug-ins that come pre-installed with Safari (Flash, Quicktime, Java, Quartz Composer, etc.).
I've also tried creating a new user account just to test this and experienced the same slowness.
There were quite a few significant updates recently - Safari 5.0.4, Mac OS X 10.6.7 and a Java update too, if memory serves -, so I can't really say that the problem lies with Safari 5.0.4, but I wonder if anyone else is experiencing the same issues.
Safari's overall performance is still fine, browsing is fast and most of the time I won't notice any issues, but this just makes the issues I DO experience all the more noticeable.
Maybe nothing has changed and everything is as it was before.
But then... why would Safari take 3 or 4 seconds to do a simple thing like tabbing between input fields on a simple website like Gmail's login page?
This and the fact that I do feel that things have slowed down somewhat is what makes me think that there is more afoot here: a broken Java update, a change in Safari's code, a buggy spellchecker daemon, something!
So if anyone is experiencing the same or feels that Safari's performance is different, I would appreciate any feedback!
Any suggestions as to how I might pinpoint the source of the problem are also very welcome.
Cheers.

Answer 1

Apologies for the long absence of a reply. I wanted to get a bit more usable data regarding this problem. Despite the helpful replies so far, I understand that I probably didn't give you much to work with.
Judging from timothies's post, I might not be going insane after all (or at least I'm not the only one).
I think I may have narrowed it down to a problem with Java and/or JavaScript.
Today, I was happily browsing with about 9 or 10 tabs open when Safari's CPU usage spiked. When there is a problem with Safari (on Mac OS X) or its performance slows down, Flash is the usual suspect, so I went to Safari's preferences and disabled it. All embedded Flash elements were immediately switched off on the pages I was browsing, but my MacBook still sounded like it was jetting off somewhere.
And here's the kicker: I had a look in Activity Monitor and it was the actual Safari process that was registering >100% CPU usage. I switched Flash back on in the prefs and, sure enough, the Flash Player plug-in process started using some CPU power, but nowhere near Safari's usage.
I went back to Safari's prefs and this time decided to disable both Java and JavaScript and Safari's CPU usage immediately dropped to a steady 5-6% and the fans slowed down.
The funny thing is I'd noticed this happening before recently. My MacBook's fans would come on all of a sudden, Flash videos would start skipping, as would general browsing (scrolling, opening tabs, etc.). I would open Activity Monitor and Safari's CPU usage would be somewhere between 90-100%, but so would Flash's. Until today, I hadn't been able to isolate the cause of the high cpu usage and had just assumed it was the Flash plug-in somehow having an impact on the Safari process. Closing a few websites would usually be enough to bring both down.
There may be other problems afoot, but I do find it interesting that I started noticing the problems in my first post after an update to both Safari AND Java. Timothies's post also seems to point in that direction. I even notice the slowness when typing this post and these forums use bloody Java too!
Is there any way to diagnose an issue with Java and/or JavaScript (a memory leak, something)? I took a sample of the Safari process while this was happening, but can't make heads or tails of it, so any help would be much appreciated.
Cheers.