I switched to Vonage about 1 month ago at home, and have been quite impressed. I switched from DSL to cable modem, because Charter was offering a good deal (2 months free & free installation) plus it was $10 cheaper per month and nearly 3 times the speed (2Mb service from Charter)
Now I only pay $15 per month for phone service, plus an additonal $5 for a virtual number (in another area code so family can call me locally). I get all the features you'd want, plus I get an e-mail at work whenever I get a new voice mail message, which I can listen to on-line or through the e-mail!
Even on long calls (1+ hours) I have no hiccups in the call, so nobody would ever know the difference (land-line vs. VOIP).