I say have or deployed as opposed to use, because most CRM in tech companies is bought by the owner, a non-sales person, who wants to reduce swivel chair and to have the system connect to everything like single sign on is a thing. You have to ask yourself: what is the CRM for? 3 things.
One, the salesperson to record his activity. That is first and foremost. If the salesperson won't use it because it is clunky or has bad UX (user design), then the system will be a failure. Also, when the salesperson leaves your company, you want to have all the contacts and data about your prospects, customers and funnel. All of it in the CRM. [see here]
Two, monitoring the funnel and salespeople daily and weekly activity. If there isn't a simple way to see what the salespeople are doing, then the CRM is worthless to management.
Three, a tool for valuation. Without a CRM, investors won't value your company. Good business requires systems. CRM is a system to see customers, funnel, contracts, prospects (market size), etc. So if you ever want to sell, use CRM.
CLECs and ISPs tend to build their own or use an open source platform like SugarCRM, although I would advise against clunky software. You need a good GUI (user interface) that makes it easy for the salespeople to use. In many cases, it has to be mobile accessible too.
MSPs tend to use the platform of their business like ConnectWise or Autotask. Clunky. You can use another system and do some swivel chair.
IDEA2 has an answer for the clunky CRM interface -- use Slack as your interface! IDEA2 just launched Sasquatch. You can easily build a CRM system using the IDEA2 platform with if-this-then-that functions, build an API, and connect the system to Marketo, Mailchimp, Gmail, etc. It is the wave of the future: business-functions-as-a-service. Cloud 2.0 if you will or at east SAAS 2.0.
Because everyone wants the CRM to connect, check the available API integration. Zoho has a lot. Some telecom agents use SalesReach with Salesforce - lot of integrations, seems like overkill (or overpay) to me, but it works for them.
There are a lot of CRM systems out there. Simple ones that work for small business like Real Simple or Batchbook or Insightly. Contactually seems more like contact management system for an online business than a full CRM. Depends what you need.
I don't talk about the big ones like Salesforce or MS Dynamics because it seems like overkill for most of the service providers I work with. However, if you are a Microsoft shop, Dynamics would seem to be an avenue to examine.
There are 9 alternatives including Nimble, Pipeline and Pipelinedeals.