I've been telling people to wait if they can until the dust settles. Well, the dust is pretty much settled. The FCC will be selling off the 600 band; even though the impact may not drift down to us until as late as 2018.
And the digital systems are starting to appear from name manufacturers, and we're almost over the hump of high prices and teething problems of new technologies. Within a few more years I expect digital will drop down in price to similar to what analog systems had been (they are cheaper to make, but the manufacturer can -- for at least the next few decades -- charge more for them because of the enhanced options.)
For the longest time I've been praising the Sennheiser packs. They are built like bricks (metal construction), you can cram 16 units into a frequency band, and they are fairly immune to anything but, well, Shure mics operated in their vicinity (not even on similar frequencies -- mid-range Shures seem to overmodulate and take a larger footprint than you would think).
The worst weakness of the Senny's is the connector to the element, but this is a weak point in all mics -- for me it is a toss-up between the locking mini of the Sennys and the TA4 of the Shures. One caveat; you need sound techs who pay attention and will screw the Senny's back down every now and then. If they do, the screw-on will outperform the TA4. If they don't -- the TA4 wins by default. Both can be aided greatly by added strain relief, done variously with tape and moleskin.
If you simply must go analog, the G3 series is still a no-brainer at the mid-range. If you have the bucks, then Shure UHF or one of the really high-end systems. If you are looking at 500-800 a channel, then the G3 at 600 bucks a channel outperforms the SLX and is (according to a rough weighting of the commentary threads at Control Booth) a bit ahead of the ULX.
For my mind, the Senny wins hand down for stage musicals; not because the ULX has a plastic case, but because it runs on (shudder) 9v. Those have less juice and cost more than AA, and are less common in rechargeables.
(As an aside, there's a chorus of people who crow constantly that rechargeables can never be used for stage musicals. Their reasons are three; that they can't be sure the battery got back in the charger every night, that there's no spare available if you do forget, and that the "gas gauge" gives a misleading reading. All of these are trivially wrong. For the last -- flip the internal switch to rechargeable and the meter will be accurate. For the other two...the critics are imagining a situation in which each mic has its own pair of batteries and there are exactly as many as there are mics. Yes; if you did this it would be a recipe for problems. So you don't. You treat the batteries in bulk and you have double the number, plus a margin. During a matinee, the evening's batteries are already in the charger, and between shows you swap them out.)
(And beside...if your crew is so lame they might forget the batteries, then why are you trusting them to check elements, mute switches, condoms, and otherwise make sure the mics are ready to go? This doesn't speak, to me, of problems with rechargeables. It speaks to a poor approach to prepping mics that is going to give you endless problems with broken elements and other technical issues. Popping in fresh batteries is mandatory no matter what you use, and it is only one of the checks each and every mic must see each and every performance).
Anyhow, the paradigm has changed. My recommendation if you must purchase microphones now is Shure ULX-D. These are 1.5 to 2x what you'd pay per channel for G3s, but they will get you 30 channels to a frequency band and will see you through the coming FCC sell-out.
Plus ethernet access is becoming more and more an essential tool. The G3 series 300 added this, and the 500s make it better, and the UHFs have it in spades. And of course the ULX-D; making full use of the digital channels comes with networked coordination and control.
I'll probably change my mind when I've had a chance to look over a Sennheiser digital, but right now the ULX looks to break the "if it has an X in the name, don't purchase it" rule for Shure mics.