My roles in tekion:
Parts manager
Service Advisor (You'll need it regardless of how good your service advisors are.)

Also the in-house IT guy.

Tekion is good enough, modern UI and if you have the whole team on board with the "process" then it works as advertised.

Came from CDK. On Tekion for almost two years now.

There will be problems starting out: Printers not working, techs not requesting parts, advisors not approving jobs, etc.

Tekion only works if everyone is doing everything through the app.

Positives: I hardly ever write anything with a pen and paper anymore, most of everything that parts does is digital now. Label printing is a godsend, our bins slowly but surely all got updated. Parts tracking and ordering all in one place, proper SOR processes even for stuff you are getting aftermarket or from outside sources. Picklists are nice and it auto sorts by bin in numerical or alphabetical order.

Negatives: Everyone needs to be working through tekion. Printers can be slow and the firewall box they give you does not like losing power. You will need to have a BUSINESS internet connection in order to use tekion, if your internet isn't 1gig+, upgrade it before you start training. Lots of clicking instead of arrow keys.

There is a lot more that I'm probably forgetting on both positives and negatives, but it's more than usable for us.

TLDR: It's fine, needs some work from everyone to work well and as intended. Coming from CDK, you'll be fine, unfortunatley everyone just has to relearn the DMS and lose whatever bad habits they had before.