Expression blend is a pure microsoft design purpose studio. The core usage of Blend is to assist Silverlight Developers & designers.
Silverlight was introduced as an RIA technology. The core feature is code separation. The View - model are in separation. Blend provides rich support for designing your silverlight apps. which may not be possible with Visual Studio 2010.(btw we are talk of advance designing - something gradients, storyboards, template controls blah blah..). It also contains application prototyping tool called sketch flow. Well Blend also contains code editor. For the designer to dive into code for more grip on designing and behaviors ( designing perspective). Yah but blend don't support advance development tools, like debugging, project source control etc....
If your company is just giving a start to Silverlight project you should be considering the project you have on development - Are they UI specific or simple basic layouts can be fine and yes there professional blend developers out there which can be hired. But still rare, count have increased after SL 4 release.
Regarding your question in specific
1. Do you find Blend easy to use? - yeah easy for me or someone who know and hard for who have opened it for first time. But trust me if using and learning how to use Visual studio is easy then Blend is the same.
2. Do you have a designer in your company that's using it (and how is he satisfied), or the developers are designers themselves? If the project have UI specific requirement - very much flashy - lots of animations etc etc then yes there are designers to do that - else developer can do the job if not affordable. Technology is new (compared to other RIAs like FLASH) so still cannot comment on SATISFACTION part.
3. Would you recommend in general using Blend to design user interface? yes very much but keeping costing and need in mind. (Eg: There are many companies who have their own wrapper framework - which include their own set of controls to be used in DA and Web Apps) Silverlight can be treated as same - can make you own custom set of controls according to your company need (eg: telerik, there another one which is famous but cant remind its name sorry)......
Hope it helps,