At what point does a company need features a UC system offers?

A very simple answer ... UC is not a system. UC is the bringing together of elements such as Voice, Email, Webchat, SMS, Instant Messaging etc. all of which can be from different vendors, therefore UC is the "glue".

When a company has multiple ways that it's customers want to make contact with it, and vice versa, then you will need a UC strategy.

The benefits to using UC are saving money by increased 1st call resolution and improving customer service.

Richard

I'd like to add to Richard's answer by saying since UC is the "glue", you don't need to attach every aspect of UC to your system, either at once or ever.

Each attachment has a dollar price associated with the purchase, so you need to ascertain for your organization and your customer and vendors which feature, be it Voice, Email, etc will give you better relationships for the bang (ROI).

On the flip side, you need to protect your employees from information overload, which is unfortunately a byproduct of our Information Technology-centric age...

Wayne

You can answer that question best. You need to learn and understand your company's business, and what they do, day-to-day. Then learn UC capabilities and figure out how they can be applied in your company to help business folks conduct business better and faster.

I suggest reading the following free papers;
'Finding the Value in Unified Communications— Understanding the Hierarchy of Return' (from Frost & Sullivan)
'Seeing Beyond the Numbers on UC' (from IT Business Edge)

Find these items free as well as many other free items that you may find helpful at;
http://www.freeknowledgenetwork.com/telephony.html

Good luck!
Tim

Wayne and Steve are headed in the right direction, but I would suggest that UC is not really the "glue", it is a strategy. And if you remember that UC solutions are developed to address real businss problems or issues, there is no "right time" or "wrong time". I would encourage any company to talk with a solutions integrator who has the proven ability to identify areas of your businss where a UC solution of some sort could help you increase sales/revenue, make you more competitive, increase customer satisfaction, control expenses, improve staff productivity or meet the communication demands of those young people now entering the workforce. Yes, UC solutions can touch any of these needs....
Last but not least, UC solutions are applicable for any size business - small to enterprise - and for most vertical markets.

I agree with Pamela that UC is a strategy one that any size organization can implement. As for the question; At what point is it worth it to invest in these features? is it company size, size of a sales team, number of locations? the answer is any/all one of these.
The accommodating feature of UC is that you can start with a single service, such as voicemail or conferencing, and upgrade your system to accommodate your needs and number of seats. UC will add immediate value to your sales team and their ability to connect via social business but it also represents a strategic investment into the future growth and competitiveness of your company.
Two articles addressing UC:
1. 10 Benefits of Acquiring Social Business and UC http://bit.ly/hC1M3x
2. Enabling Employees with UC http://bit.ly/gSOwQ7