For the past year IBM has been huffing and puffing to gain acceptance for its latest line of personal computers. Now it may have crested the hill.

Since International Business Machines Corp. introduced Personal System/2 in April 1987, its competitors have gained market share by selling computers compatible with IBM's previous line. To boost PS/2 sales, IBM stopped selling its own earlier models. Customers responded by selecting clones made by companies such as Compaq Computer Corp., Zenith Data Systems and Dell Computer Corp.Industry analysts flayed IBM for abandoning its old standard, for confusing computer products companies about its licensing policies and for selling a new, costlier system with few obvious benefits.

Now, after months of criticism and bad publicity, IBM is getting some vindication. "I think it's definitely turned the corner," says Richard Shaffer, editor of Technologic, an industry newsletter. "I get a sense that sentiment is moving in IBM's favor."

"There's beginning to be a feeling in the industry that IBM is going to be hot in 1989," says Stewart Alsop, publisher of PC Letter.

IBM's risky bet on a key piece of hardware called Micro Channel is paying off. Micro Channel - the key difference between PS/2 and the earlier PC - is a bus, the electrical roadway that connects a computer's various parts. IBM bestowed Micro Channel on some of its PS/2 machines and claimed it was the wave of the future.

Yet companies that make desktop computer clones were confused about whether they could license Micro Channel technology to build compatible systems. More troubling, IBM seemed unable to explain its benefits. There was also an initial drought of add-on products from other companies. Taken together, this situation made customers balk at IBM's PS/2. As the giant company battled industry skepticism, nine rival firms formed a consortium called EISA (Extended Industry Standard Architecture), promising computers more powerful than PS/2 using a bus they are developing.

Now sales of PS/2 computers with Micro Channel are picking up. According to Storeboard, a Dallas market research firm, Micro Channel-based computers' share of the desktop markets rose from 17.7 percent in the first quarter of 1988 to 20.9 percent in the third quarter. In contrast, the market share of the older IBM standard dropped from 68.3 to 61.4 percent.

Since these figures do not include IBM's sales directly to corporations, which account for about 20 percent of its unit sales, IBM's actual market share is probably higher, a Storeboard spokeswoman said.

IBM says it has shipped more than 3 million PS/2 machines, more than half of which are Micro Channel-based systems. Several factors account for the turnaround.

First, IBM improved its approach to licensing. Whereas before third-party licenses seemed expensive and hard to get, IBM now pushes them aggressively. "Anyone who wants a license can come forward and we'll give you one," said Robert Carberry, IBM's Entry Systems vice president.

As a result, the prospect for Micro Channel clones is brighter. Indeed, industry sources indicate some major computer makers are now preparing clones that could appear on the market during the next several months. So far, only Tandy Corp. has been selling Micro Channel compatibles.

And, as a result of cloning, add-on manufacturers should benefit.

"It'll give us an opportunity," said Martin Soble, marketing vice president of Orchid Technology in Fremont, which makes graphics add-on boards for PCs. "Someone loyal enough to buy a computer from IBM is likely to buy add-ons from IBM but the clone buyers' loyalty is zero. So they'll buy from us."

According to IBM, 600 PS/2 products have resulted and new ones are being introduced at the rate of 40 each month. If the trend continues, it could lead to the same kind of cottage industry in add-ons that grew up around the original IBM PC.

The proliferation of add-on boards has helped IBM. Since these products bring extra features such as networking and co-processing, the PS/2 line has become more appealing. And the increasing number of Micro Channel sales encourages companies to develop other products.