The KT77 tester has proved very popular. I can't really comment on what it's like to use in the field as we only use our KT77 to help provide support and test items around the office to develop the SimplyPats software.
If you are a facebook user you may want to post your same question on the Pat Testing Network page as there are alot of experienced testers who may already have that particular tester.viewtopic.php?f=47&t=809
The KT77 is based around the Seaward Europa so has a proven track record. One great advantage it has is the ability to download data to a memory stick which can be a real time saver and hassle free as it's cuts out any issues of connecting the tester via cable to your PC.
What ever tester you buy you can get an additional discount from some of the online retailers by being a member of this forum.viewtopic.php?f=14&t=633