I read a bunch of messages about rear derailleur quality. Comparing Deore to Alivio, I read Deore does better in difficult situations and didn't need to be adjusted as often.
As for durability, I read a message from an ultra cyclist here saying high-end components do not last longer. I think it depends which components though. I mean a crankset with alloy chainrings on Deore may not last as long as steel chainrings on Alivio. And Deore LX hubs may last longer than Deore or below.
I wouldn't have a problem with lower end components mixed with a higher end rear derailleur. Sports Experts had a bicycle for example with Shimano Altus front derailleur, Shimano Acera rear derailleur and was on sale for $279 with a regular price of $350. I just thought this was great. I felt like replacing my Canadian Tire bicycle for that Diadora bicycle right away. I didn't have the money to do it though.
I think it's pretty obvious the rear derailleur gets used more often than the front derailleur. So I think it's a great way to save money if you wanted a rain/city bike that still works well.
As far as I know, Shimano Acera and Shimano 2300 (road) is acceptable. But, Deore is a higher step up than an incremental improvements. Also, there is apparently less difference between Deore and Deore XT than there is between Deore and Alivio.
I have to admit though, if I wanted to buy a cheaper bicycle like the Diadora Palermo, I would have been tempted to switch the shifters to Falcon friction shifters so I wouldn't have to adjust the derailleurs as often. Friction shifting from what I read is more compatible with an 8 speed cassette or less.
Last edited by hybridbkrdr; 10-09-11 at 10:36 AM.