Most of us here think Voom is great -- once you get past the install. No question about it.
My "free install" ended up costing me over $400, all said and done. "Oh, you want us to use a ladder? That will be an extra $90". "Oh, you don't want phone wires running along your walls? That will be an extra $50 for a wireless phone jack." "Oh, you want us to crawl under your house? That will be....." You might want a safe power strip, Etc., Etc. Then there are charges for a larger OTA antenna, etc., as you say.
So, my advice, go look at the program listings at zap2it.com and make sure you like the Voom programming. Also, go to antennaweb.org and make sure you are in a location to receive all the OTA channels you are expecting.
If you are happy with the programming and the OTA reception in your area, and if you really want to have a ton of HD (not available anywhere else), then bite the bullet and go for it!
We have been with Voom since May and we really like it.