VOIP - To Do or not to Do?

"Jump in the waters fine", thats what everyone keeps telling me about VOIP. My company is at the point where I believe VOIP may be what we need, however... (that "however" always pops up doesnt it). Being an old telecom guy, I like "Tip & Ring" not dot.dot.dot.dot, so I guess Ill have to get use to it.

The new business we are starting needs some creative telecommunications. We have 2 sales engineers that can be anywhere in a 200 sq mile area on cell phones. They will not have internet connectivity all the time except at home (100 miles from office). I am thinking about getting a small VOIP system for our office that can do the following:

1. Voicemail
2. call transfer to our sales guys cells
3. Incoming/outgoing fax (probably thru pots line)

What are some of the better products many of you have worked with - for a decent price?

Thanks!

Jim Speed
IT Mgr,
NYTE Solutions