Sequence Vs. GUID

Question

I'm looking for an opinion or past experiences with using GUID's instead of sequences for generating unique identifiers in a system.
I like the fact that GUID's are unique in a distributed environment so we wouldn't have to worry about syncronizing indexes among environments.
I also like the fact that the app server or the DB or anyone else can generate a GUID and it will be unique.
I've done some benchmark with GUID's and the only thing that concerns me is that index sizes seem to grow quite large, especially for composite indexes. I've used RAW(16) and VARCHAR2(32) as datatypes. RAW was better than VARCHAR2 but still much worse than NUMBER (generated by a sequence).
Queries based on a GUID compound index required about 3 times as many consistent gets.
I worry that GUID's may not scale in a system that depends on a lot of composite indexes for it's queries.
Any comments, past experiences, or opinions will be helpful.
Thanks.

Answer 1

I have only once worked with GUIDs in SQL Server to support a very badly written application. When I had to debug some crazy SQL statements, it was much pain to query sample data using these crazy GUIDs.
For normal sequence generated numbers I as a debugger could easily:
1) type it and probably even remember them temporary for a little while
2) compare them and see that THIS field has different value than THAT field, which actually should be FK to THIS field
For GUIDs I could only CTRL-C, CTRL-V them, and compare was really pain for eyes.
Of course normally generated GUIDs and IDs aren't shown to any user, so probably this isn't a very big argument, but this pain is still in my mind :))
Gints Plivna
http://www.gplivna.eu