Van Engelen is highly regarded. Very positive reviews. And the selection is impressive.

I haven't used them personally yet, but I may be doing so this season. I can find 95% of the bulbs I am looking for locally, so rarely mail order. But VE's prices, especially when ordering in volume, are much better than I can get with my local retailers.

'Rare' means different things to different people so without specifics, that's hard to evaluate. But they do carry a wide range of less common bulbs, which are really what I focus on.

Van Bourgondien sells good bulbs at wholesale prices.

I use Van Engelen/John Scheepers for most things. They usually are pretty good. For speciality stuff, I use odysseybulb.com, his stuff may be a bit expensive, but it never fails and is always delivered in excellent condition (some bulbs dont' tolerate the kind of handling of a large commercial warehouser and dry storage).

I have used Brent and Becky without any issues. Also Easy to Grow Bulbs has been fine. For unusual I second Odyssey and would suggest Telos Rare Bulbs.

I have used VE in past when I could handle a large quantity..