I migrated to Zen after hearing of their reputation for reliability/good tech support - and after having a dreadful time with my previous ISP trying to get them to look into a fault that caused essentially complete loss of connectivity.
The fault didn't resolve by itself during the migration. There were some hiccups on the first day or two of the account, but Zen tech support swung into action and very quickly resolved the pre-migration problem.
Actually, the total time during which the problem was resolved with Zen (with about 10-12 emails and 6-8 phone calls involved in a tricky fault diagnosis over several days!), was the same as the time to make my very first contact with an engineer on my previous ISP.
The Zen techie that resolved the problem was extremely communicative, polite and helpful - excellent to deal with (I say this as a former tier 2/3 techie myself).
Now, I have the same sync speed as before - as expected. But, I think the internet connection with Zen is faster overall in terms of download/upload speeds, particularly in the evenings, though it's early days. I'm not certain but I know I've seen 550kB/sec speeds in the last few days, when the best I've had this year was probably 300kB with the previous ISP.
The price with Zen is about the same as what I was paying before for slower speeds and seemingly-absent outsourced tech support on the old ISP.
So, a big thumbs up for Zen. Keep up the good work