I read a 2016 review from CPA Practice Advisor on 8 sales tax programs, including Avalara. It was geared toward CPAs, so it may not have included everything, although in searching on-line, I did not discover any others. AvaTax did have the highest rating of 5.0 stars. Others at the 5.0 star level were CCH SureTax and Thomson Reuters ONESOURCE Indirect Tax. Most of these do not have an easy, seamless connection to accounting software like AvaTax does. AvaTax is still the best for integration.
You need to have contacts at the sales level from Avalara, as @ThereseLogeais mentioned. Sales and account people are readily available (because they always assume there is a new sale on the other end of the line) and they do not want issues because it's bad for business, so they can get you to whoever you need.