I'm looking to purchase a wireless lav system for my XL2 and was wondering what the major difference between UHF and VHF systems are. The UHF systems seem to be a lot more expensive. The mic will be primarily used for interviews in quiet areas, so there's not going to be any long distances between the mic and reciever.

Distance isn't the only issue between the two frequency types. Interference with VHF systems is much more likely. Diversity systems are CRITICAL with VHF.
DTV can also play havoc with wireless' so that alone is another great reason to look closely at UHF.

This isn't to say that VHF is useless, it's just to say that problems are more likely, but you also might be working in an area with little interference, and things will work just fine with a cheaper unit.

I too need to make the jump into wireless. I've been borrowing from some friends and am now ready to purchase. I do weddings with two PD170's. I have a Berringer MXB1002 board I use to get my feed from the church sound system and my mics then feed it to the camera. I am in a very rural area. We have one FM radiostation in in the county. The closest broadcast TV station is more than 60 miles away. Doug, from what you've said it looks like I could go for a true-diversity VHF system without too much concern about interference. I plan on getting three but would include at least one Sennheiser G2 to have UHF with the other two being VHF. Is this a "sound" plan? (pun intented... :-) )

On second thought, for a hundred dollars more than the above setup I could just get 2 G2's. Sure would be nice to have three beltpacks though. I want to stay under $1000 for wireless sound. Not much work here in the boonies to pay for lots of frills. :-) Gotta stick with the basics for now.

The G2s might be cheaper in the long run if the alternative uses 9V or more expensive batteries.

In Canada, AA batteries are like fifty cents each versus $2 for 9Vs. Not sure which lasts longer, but wireless systems generally guzzle batteries. The total cost of a wireless system may be something which you may wish to consider.