I see that Venton has worked on drivers, but T2 not working in here yet. I now tested with agonis-4.3-uniboxhde-20150331 (with 28/02/15 drivers) image.
No slowness in autosearch (or system operations) or problems with channel changes noticed with this image.
I recognized something that might explain the problem. I noticed that the code rate used in here (4/5) for DVB-T2 is not available even in the manual search selection. Here is an link to the Finnish specification that I found (page 20):
Code:
http://www.digita.fi/files/1160/Finnish_DTTV_RoO_versio_1_1_final.pdf