A few years ago when I was looking at new receivers, Digital was all the rage. Now I never see them where'd they go? Just not catch on or was it something else?

(I'm assuming your talking class d?)
I know. I've been following these since they came out, and it's so hard to find the less expensive receivers in canada, now, as well.
BB/FS stopped carrying them too.
Here's what I know so far.
Panasonic has put out a mess load. They have QUITE a strong following, especially in the states.
They've already been through the saxr-10, 45, 30, 50, 70, 55, 57, and now 700.
There's a dude named GoldenEar on the avs forums who's seen the upcoming xr-707 at a CES show (no official press release on it yet though).
Harmon Kardon came out with one (avr-2005?), that critics met with a so-so verdict, and was over priced.
JVC put out a couple that seem to be on Pannie's level, although the earlier guys ran a little hotter and seem have more glitches. I think these are getting up to speed though.
Kenwood put out a couple models a year or 2 ago, but need to get back on the ball.

on the higher end of the spectrum, there's more and more companies starting to cultivate the technology. Rotel has been working with B&O to put out there ICEpower stuff, and it's getting wild reviews. they're saying that some of the amps that measure 100w/channel are equal, if not, better than their 200W analogue counterparts. Good stuff.
here's a list of all the companies who are currently manufacturing amps based on class D tech.
http://www.avsforum.com/avs-vb/showthread.php?t=594707&highlight=digital+ht+receiver+list

i think some people are deterred by the lower power ratings?
Or maybe its just the old fear of new technology.
I like it though. Those panasonic receivers are worth they're weight in gold. Amazing clarity and accuracy from something so small.
I'll be upgrading mine again shortly, and staying with panasonic.
(need more HDMI inputs!)

Or maybe its just the old fear of new technology

While digital amps offered lower running temps (and hence lower energy usage), the mid fi class D amps were thought to suffer from soundstage (or lack of such) issues + bass response when compared to similiarly priced competitors.

I'm not so sure about that.
Bass response is largely improved on their A/B counterparts.
That's why they mostly use class D on subs.
And accuracy and clarity i mentioned before, contribute to a GREAT soundstage.
I think if there's a potential weakness in these systems, its brightness.
Some folks aren't used to the detail.